Porous inorganic solids have found great utility as catalysts and separation media for industrial application. In particular, mesoporous materials, such as silicas and aluminas, having a periodic arrangement of mesopores are attractive materials for use in adsorption, separation and catalysis processes due to their uniform and tunable pores, high surface areas and large pore volumes. The pore structure of such mesoporous materials is large enough to absorb large molecules and the pore wall structure can be as thin as about 1 nm. Further, such mesoporous materials are known to have large specific surface areas (e.g., 1000 m2/g) and large pore volumes (e.g., 1 cm3/g). For these reasons, such mesoporous materials enable reactive catalysts, adsorbents composed of a functional organic compound, and other molecules to rapidly diffuse into the pores and therefore, can be advantageous over zeolites, which have smaller pore sizes. Consequently, such mesoporous materials can be useful not only for catalysis of high-speed catalytic reactions, but also as large capacity adsorbents.
It was further discovered that the inclusion of some organic groups in the mesoporous framework can provide adjustable reactive surfaces and also contributes to uniformity in pore size, higher mechanical strength, and hydrothermal stability of the material. Thus, mesoporous organosilica materials can exhibit unique properties compared to mesoporous silica such as enhanced hydrothermal stability, chemical stability, and mechanical properties. Organic groups can be incorporated using bridged silsesquioxane precursors of the form Si—R—Si to form mesoporous organosilicas.
Mesoporous organosilicas are conventionally formed by the self-assembly of the silsequioxane precursor in the presence of a structure directing agent, a porogen and/or a framework element. The precursor is hydrolysable and condenses around the structure directing agent. These materials have been referred to as Periodic Mesoporous Organosilicates (PMOs), due to the presence of periodic arrays of parallel aligned mesoscale channels. For example, Landskron, K., et al. [Science, 302:266-269 (2003)] report the self-assembly of 1,3,5-tris[diethoxysila]cyclohexane [(EtO)2SiCH2]3 in the presence of a base and the structure directing agent, cetyltrimethylammonium bromide to form PMOs that are bridged organosilicas with a periodic mesoporous framework, which consist of SiO3R or SiO2R2 building blocks, where R is a bridging organic group. In PMOs, the organic groups can be homogenously distributed in the pore walls. U.S. Pat. Pub. No. 2012/0059181 reports the preparation of a crystalline hybrid organic-inorganic silicate formed from 1,1,3,3,5,5 hexaethoxy-1,3,5 trisilyl cyclohexane in the presence of NaAlO2 and base. U.S. Patent Application Publication No. 2007/003492 reports preparation of a composition formed from 1,1,3,3,5,5 hexaethoxy-1,3,5 trisilyl cyclohexane in the presence of propylene glycol monomethyl ether.
However, the use of a structure directing agent, such as a surfactant, in the preparation of an organosilica material, such as a PMO, requires a complicated, energy intensive process to eliminate the structure directing agent at the end of the preparation process. This limits the ability to scale-up the process for industrial applications. Therefore, there is a need to provide additional organosilica materials with a desirable pore diameter, pore volume and surface area. Further, there is a need to provide such organosilica materials that can be prepared by a method that can be practiced in the absence of a structure directing agent, a porogen or surfactant.